Larval Survival Research Articles

Asian seabass (Lates calcarifer) larval rearing using cyclopoid copepod (Apocyclops royi) live feed: A new approach

BackgroundThe Apocyclops species are gaining importance as suitable live feed for augmenting growth and survival of marine finfish larvae. In the present study, as a new approach Apocyclops royi is mass cultured using monoalgal diet (Chloroidium saccharophilum) and its nutritive value is assed and used as supplementary diet in the Asian seabass Lates calcarifer larval rearing.ResultsMass culture of A. royi with C. saccharophilum diet reached population density of 12,700 ± 454 ind./L on 21 days culture period. A. royi showed high ratio of DHA:EPA and EPA: ARA. Rearing experiments of the Asian seabass (Lates. calcarifer) 11 DPH larvae with copepod, Artimia nauplii and their combination diets recorded faster growth and maximum survival (90%) with A. royi + Artemia nauplii diet compared to A. royi and Artemia nauplii lone feeds. Seabass larval length and weight gain showed significant (p < 0.05) difference among the three dietary treatments. Significantly high content of essential fatty acids in the L. calcarifer larvae have been reported in A. royi + Artemia nauplii fed seabass larvae compared to individual A. royi and Artemia nauplii fed larvae.ConclusionsOur finding highlights the importance of incorporating A. royi as a supplementary feed for seabass larvae, which will bring improvement in their growth and survival leading to sustainable seed production of this fish.

Characterization of probiotic Bacillus sp. NP5 metabolites and its effect on female catfish broodstock rematuration

Probiotics are believed to contain active components that affect fish reproduction. This study aimed to evaluate the metabolite compounds contained in the probiotic Bacillus sp. NP5 and its effect on female catfish broodstock rematuration. The first step was to analyze the metabolite content of probiotic using liquid chromatography with tandem mass spectrometry LCMS/MS. Furthermore, feed supplementation was implemented with probiotic at concentrations of 106 CFU g-1 (P6), 108 CFU g-1 (P8), and control (C). Parameters observed included metabolite content of Bacillus sp. NP5, gonadosomatic index (GSI), hepatosomatic index (HSI), gonad histology, gonad maturity rate, fecundity, number of matured eggs, distribution of egg diameter, fertilization rate (FR), hatching rate (HR), larval survival (SR), rematuration period, and percentage of matured broodstock. The results showed that metabolites such as resveratrol (22.45%) and indoline (7.11%) are probably directly affecting reproduction. Other metabolites such as oxyresveratrol (22.95%) and vestitol (4.14%) are also thought to play an indirect role. Supplementation results showed the best reproductive performance in 108 CFU g-1 feed treatment with an increase in GSI (14.74%), HSI (1.65%), gonad maturity rate, percentage of mature eggs (86.00%), rematuration period (4 weeks), percentage of matured broodstock (100%), fecundity (243605.02 eggs/broodstock), FR (98.74%), HR (80.62%), and SR (87.31%). Application of probiotic Bacillus sp. NP5 can accelerate rematuration and improve reproductive performance of female catfish broodstock. Probiotics contain metabolites that have a positive effect on reproduction and can be an alternative in improving reproductive performance in female catfish broodstock. Keywords: Bacillus sp. NP5, female catfish, metabolites, probiotics, rematuration

Macronutrient-Based Predictive Modelling of Bioconversion Efficiency in Black Soldier Fly Larvae (Hermetia illucens) Through Artificial Substrates

This study explores the optimisation of rearing substrates for black soldier fly larvae (BSFL). First, the ideal dry matter content of substrates was determined, comparing the standard 30% dry matter (DM) with substrates hydrated to their maximum water holding capacity (WHC). Substrates at maximal WHC yielded significantly higher larval survival rates (p = 0.0006). Consequently, the WHC approach was adopted for further experiments. Using these hydrated artificial substrates, fractional factorial designs based on central composite and Box–Behnken designs were employed to assess the impact of macronutrient composition on bioconversion efficiency. The results demonstrated significant main, interaction, and quadratic effects on bioconversion efficiency. Validation with real-life substrates of varied protein content, including indigestible feather meal, affirmed the predictive model’s accuracy after accounting for protein source digestibility. This research underscores the importance of optimal hydration and macronutrient composition in enhancing BSFL growth and bioconversion efficiency.

Salinity-dependent effects of integrated biofloc technology on reproductive performance, biological responses, and offspring quality in red tilapia aquaculture

The study aims to evaluate the reproductive performance, serum biochemical indices, growth, antioxidant capacity, and immune response of Florida Red Tilapia (Oreochromis sp.) progeny reared at different salinity levels within biofloc technology (BFT) systems, focusing on egg production, fertilization rates, tolerance to oxidative stress, and offspring performance. Broodstock reared in biofloc systems (BF) were compared to those in clear water (Without biofloc, WBF) across three salinity levels (18, 28, and 36‰) over a 7-month period. The study also assessed the tolerance of fry reared in biofloc systems to direct transfer to high salinity (36‰) without prior acclimatization. A total of 216 females (initial body weight: 182 ± 1.8 g) and 72 males (initial body weight: 201 ± 0.88 g) were randomly assigned to 18 concrete tanks (2 × 6 × 1 m) to investigate the effects of BFT on spawning performance and larval survival under high-salinity conditions. The findings indicated that appropriate salinity (18‰) in BFT systems positively affected reproductive efficiency, enhanced immunological parameters, and improved growth performance, but elevated salinity levels (36‰) led to reduced reproductive success and hindered growth performance. Florida red tilapia thrive in water quality conditions that are within acceptable limits. High salinity environments led to increased dissolved oxygen but reduced pH, especially in BFT ponds. BFT improved reproductive performance, reduced spawning time, and increased egg production. It also improved hatchability, larval quality, and yolk sac absorption. The BFT broodstock showed higher levels of key proteins (total protein, albumin, and globulin) and improved immune parameters, which helped counteract the negative effects of elevated salinity and enhanced their overall health and stress tolerance. In high-salinity environments, offspring in BFT systems showed higher survival rates and growth rates. In conclusion, BFT improves the reproductive performance, growth, and immune response of Florida red tilapia under high salinity. It enhances egg production, hatchability, and larval survival, while also improving water quality and immune function, making it a sustainable solution for tilapia aquaculture in saline environments.

Land-derived metals impact the survival and settlement of larval mussels.

Global declines in wild mussel populations and production have been linked to the impacts of climate change and pollution. Summer die-offs of mussels (Perna canaliculus), spat retention issues, and a severe decline in mussel spat settlement have been reported in the Marlborough Sounds, an important area for mussel farming in New Zealand. Preliminary evidence suggests that naturally occurring contaminants and changing land use in the surrounding areas, could contribute to the decline of this species. The aim of this study was to determine whether trace metals affect the larval survival and settlement of mussels. Concentrations of trace elements in surface waters, mussel gill tissues and sediments were characterized across the Marlborough Sounds. Over a two-year period, diffusive gradients in thin film (DGT) passive samplers were deployed at three locations, to estimate trace metal levels in the water column. Mussel gills and sediment were also collected to complement metal monitoring. Lead and zinc were the most abundant bioavailable metals detected during in-situ monitoring, with strong temporal variability. Ecotoxicity thresholds affecting P. canaliculus embryo-larval development and settlement were determined for these metals and overlapped with levels of lead and zinc found in the field during the reproductive season of mussels. Furthermore, high concentrations of zinc and lead in waters were strongly correlated with rain events, suggesting land runoff in the surrounding catchments as their main source. We hypothesize that vulnerable early life stages of mussels are exposed to these metals, especially following summer rainfalls, delivering pulses of these metals into the environment while triggering mussel spawning events. Climate-associated stressors (intense storms, marine heatwaves, freshwater and sedimentation inputs, acidification) are likely to exacerbate any toxic effects from land-derived inputs; a better understanding of these complex interactions is essential to prevent further P. canaliculus recruitment declines occurring in NZ, and in other mussel species globally.

Hsf1 is essential for proteotoxic stress response in smyd1b-deficient embryos and fish survival under heat shock.

Molecular chaperones play critical roles in post-translational maintenance in protein homeostasis. Previous studies have shown that loss of Smyd1b function results in defective myofibril organization and dramatic upregulation of heat shock protein gene (hsp) expression in muscle cells of zebrafish embryos. To investigate the molecular mechanisms and functional importance of this stress response, we characterized changes of gene expression in smyd1b knockdown and knockout embryos using RNA-seq. The results showed that the top upregulated genes encode mostly cytosolic heat shock proteins. Co-IP assay revealed that the upregulated cytosolic Hsp70s associate with myosin chaperone UNC45b which is critical for myosin protein folding and sarcomere assembly. Strikingly, several hsp70 genes also display muscle-specific upregulation in response to heat shock-induced stress in zebrafish embryos. To investigate the regulation of hsp gene upregulation and its functional significance in muscle cells, we generated heat shock factor 1 (hsf-/-) knockout zebrafish mutants and analyzed hsp gene expression and muscle phenotype in the smyd1b-/-single and hsf1-/-;smyd1b-/- double-mutant embryos. The results showed that knockout of hsf1 blocked the hsp gene upregulation and worsened the muscle defects in smyd1b-/- mutant embryos. Moreover, we demonstrated that Hsf1 is essential for fish survival under heat shock (HS) conditions. Together, these studies uncover a correlation between Smyd1b deficiency and the Hsf1-activated heat shock response (HSR) in regulating muscle protein homeostasis and myofibril assembly and demonstrate that the Hsf1-mediated hsp gene upregulation is vital for the survival of zebrafish larvae under thermal stress conditions.

Plasticity of metamorphic traits in the Asiatic toad Bufo gargarizans: interactive effects of food quality and zinc pollution

Organisms with complex life cycles, like amphibians, are greatly affected by environmental factors and maternal effects, which in turn influence their morphological variation. The Asiatic toad Bufo gargarizans is found throughout East Asia and is not only valued for its economic medicinal properties in China but also considered a potential indicator species for assessing environmental pollution in inland rivers. However, the specific responses of this species to environmental toxicants, including trace metals, are not well comprehended at present. In this study, we experimentally examined the plasticity in larval period, body mass and size, and survival at metamorphosis in tadpoles of B. gargarizans under different combinations of food quality and zinc (Zn). We found that larval period, survival, SVL and mass at metamorphosis were sensitive to food quality, larval period increased significantly with increasing Zn concentration. The interaction between food quality and zinc primarily influenced the larval period. Tadpoles that were fed a high-energy diet, rich in protein and lipids, tended to have a shorter larval period as zinc concentration increased. Conversely, tadpoles fed a low-energy diet had a longer larval period with increasing zinc concentration. Thus, zinc plays a role in determining the extent to which food quality affects development of B. gargarizans. Additionally, larvae that consume a low-energy diet tend to have higher survival rates as zinc concentration increases, suggesting that moderate levels of zinc concentration (below 150 μg/L) are beneficial for normal physiological and biochemical processes in these organisms. The findings from this study provide valuable insights into the toxicological responses of this species to trace metals, contributing to a better understanding of their impact. Keywords: Bufo gargarizans, acute toxic effect, zinc, interaction effects, age and size at metamorphosis, phenotypic plasticity

Chronic Radium-226 toxicity to and oxidative stress in the aquatic invertebrate Chironomus dilutus

Abstract The mining industry, including uranium mining and milling, is of high importance in Canada. It is, however, important to consider that ore processing can result in the creation of by-products that contain radionuclides such as radium-226 (226Ra). Even with the strict discharge regulations in place, there is limited evidence to suggest that the current Canadian regulatory thresholds for 226Ra are protective for aquatic life. This concern underscores the importance of generating toxicity data for 226Ra, as no federal Canadian water quality guidelines for 226Ra currently exist to safeguard aquatic ecosystems. The potential ecological risks of 226Ra are significant due to its high mobility under typical environmental conditions, long half-life (t1/2 ~ 1,600 years), bioaccumulative properties, and similarity to calcium (Ca2+). Considering this, the primary objective of this research was to gather data on the toxicity of 226Ra to the aquatic invertebrate Chironomus dilutus. For this purpose, a partial life cycle experiment was conducted, with larval growth, survival and pupation, and emergence and sex ratio of emerged adults, as the experimental endpoints. In addition, an assessment of oxidative stress as a potential cause of toxicity was performed. These experiments revealed that elevated activity concentrations of 226Ra (25.5 Bq/L) can significantly impact the growth of C. dilutus. However, none of the other nonlethal endpoints were significantly affected by 226Ra exposure, and there was no evidence of oxidative stress in exposed C. dilutus. Finally, 226Ra was shown to adsorb onto the silica sand used as a substrate for all experiments and desorbed following acid extraction.

PHMB at 0.1% inhibits bacterial growth but does not eradicate biofilm or protect against infection in a Tenebrio molitor model

Biofilm in chronic wound is an important public health problem in several countries due its delayed healing and ineffective local treatment. Several treatments are employed to inhibit bacterial growth, among which polyhexamethylene biguanide (PHMB) stands out. PHMB is widely known for its antibacterial properties through mechanisms that include the interaction of this compound with bacterial cell walls and DNA. However, there are conflicting data regarding its activity in eradicating mature biofilm. The purpose of this study was to investigate the in vitro and in vivo anti-biofilm activity of the PHMB as well as its toxicity. Herein, we show that PHMB inhibits the bacterial growth in all concentrations, except for Klebsiella pneumoniae. We used a well-established biofilm model to quantitatively assess the eradication of organisms. PHMB at 0,1% did not eradicate biofilms of Enterococcus faecalis, Klebsiella pneumoniae and Staphylococcus aureus. In vivo testing of PHMB in Tenebrio molitor larvae infected with Enterococcus faecalis, Klebsiella pneumoniae and Staphylococcus aureus, this compound did not induce any toxicity, however it increased AST levels by around 600%. Furthermore, the PHMB did not improves larvae survival and did not reduce bacterial load in their hemolymph. We suggest that PHMB in this concentration may represent an alternative to treatment of infection in wounds, but not as a therapeutic alternative for wounds with biofilm.

Effect of thermal stress on the biological traits of pink bollworm (Pectinophora gossypiella Saunders) (Lepidoptera: Gelechiidae)

The pink bollworm (Pectinophora gossypiella) is a significant pest of cotton worldwide. Its occurrence and distribution across various cotton-growing regions are influenced by multiple factors, with temperature being a critical determinant. This study aimed to analyze the life history traits of the pink bollworm under different temperature regimes. Biological and demographic parameters of P. gossypiella were systematically examined at five specific temperatures: 20°C, 25°C, 30°C, 35°C, and 40°C, under a controlled photoperiod of 16 h of light and 8 h of darkness (LD 16:8 h). The results revealed that the total developmental period of the pink bollworm decreased with increasing temperatures, with the highest larval survival rates observed at 30°C and 40°C, reaching 78.93% and 63.89%, respectively. Moreover, pupal weight, mating success, and fecundity were significantly higher at 30°C and 35°C. In contrast, lower egg hatching rates, larval survival, and adult emergence were recorded at the extremes of 20°C and 40°C. These findings offer valuable insights into the population dynamics of P. gossypiella under field conditions and highlight the need for climate-resilient management strategies to mitigate its impact on cotton production.

Enhancing Silkworm (Bombyx mori L.) Larval Survivability Through Spermidine Supplementation

The silkworm, Bombyx mori L., is a species of great economic significance since it is essential to the manufacture of silk. Improving silkworms' growth, survival rates, and silk yield throughout their larval stages requires increasing their food intake. The purpose of this study is to evaluate the effects of adding spermidine to mulberry leaves on Bombyx mori L. larvae survival. The experimental groups in this experiment were given mulberry leaves treated with different doses of spermidine, such as Spd 25, 50, 75, and 100 µM. The larvae were separated into control and experimental groups. The findings demonstrated that larvae fed leaves laced with spermidine had higher survival rates than the control group. However, compared to the control group, the treated group's mortality rate was decreased. These findings indicate that spermidine could be a useful nutritional enhancement in sericulture, promoting better larval health and increased silk production.

Fitness costs associated with laboratory induced resistance to chlorpyrifos in Spodoptera litura

Spodoptera litura (Fabricius) is a major polyphagous pest of global relevance due to the damage it causes to various crops. Chlorpyrifos (CPF) is generally used by farmers to manage S. litura, however, its widespread use has resulted in the development of insecticide resistance. Therefore, in the present study, a population of S. litura was exposed to CPF for eight generations under laboratory conditions, resulting in a 2.81-fold resistance ratio compared with that of the unselected laboratory population (Unsel-Lab). The exposure of Unsel-Lab and CPF-Sel populations to their respective lethal and sublethal concentrations reduced larval survival, adult emergence, and prolonged development period, and induced morphological deformities in adults. The reproductive and demographic parameters were also significantly lowered in the treated larvae of both populations at higher concentrations. Moreover, hormetic effects on fecundity, next-generation larvae, the net reproductive rate (R0), and relative fitness (Rf) were observed at lower sublethal concentrations of CPF, specifically at the LC5 of Unsel-Lab and the LC10 of the CPF-Sel population. Sublethal exposure to CPF negatively affected the biological and demographic parameters in both populations, although the impact was more prominent in the CPF-Sel population. The relative fitness of the CPF-Sel was also greatly reduced at the LC50 (0.28) compared to that of the Unsel-Lab population. However, only a marginal trade-off of insecticide resistance evolution was observed in the CPF-Sel population in the absence of insecticide selection pressure. These results provide useful information for devising improved pest management strategies for CPF resistance in S. litura.

Valine Restriction Extends Survival in a Drosophila Model of Short-Chain Enoyl-CoA Hydratase 1 (ECHS1) Deficiency.

Short-chain enoyl-CoA hydratase 1 deficiency (ECHS1D) is a rare genetic disorder caused by biallelic pathogenic variants in the ECHS1 gene. ECHS1D is characterised by severe neurological and physical impairment that often leads to childhood mortality. Therapies such as protein and single nutrient-restricted diets show poor efficacy, whereas the development of new treatments is hindered by the low prevalence of the disorder and a lack of model systems for treatment testing. Here, we report on the establishment of a Drosophila model of ECHS1D. Flies carrying mutations in Echs1 (CG6543) were characterised for their physical and metabolic phenotypes, and dietary intervention to improve fly model health was explored. The Echs1 null larvae recapitulated human ECHS1D phenotypes including poor motor behaviour and early mortality and could be rescued by the expression of a human ECHS1 transgene. We observed that both restriction of valine in isolation, or all branched-chain amino acids (BCAAs-leucine, isoleucine and valine) together, extended larval survival, supporting the idea that reducing BCAA pathway catabolic flux is beneficial in this disorder. Further, metabolic profiling revealed substantial changes to carbohydrate metabolism, suggesting that Echs1 loss causes widespread metabolic dysregulation beyond valine metabolism. The similarities between Drosophila and human ECHS1D suggest that the fly model is a valuable animal system in which to explore mechanisms of pathogenesis and novel treatment options for this disorder.

Morphological and biological characterization of Spermophagus niger (Motschulsky, 1866) (Coleoptera: Chrysomelidae) from four West African countries.

In Burkina Faso and many West African countries, Spermophagus niger (L.) is the main insect pest of Hibiscus sabdariffa seeds stored with considerable damage. Variations in bioclimatic conditions can lead to significant changes in the morphology and biology of populations of the same insect species, leading to strains that are morphologically and biologically different and that would react differently to a given control method. In this study, strains of S. niger from Niger (Niamey), Ghana (Navrongo), Benin (Parakou) and five localities in Burkina Faso (Diébougou, Banfora, Saaba, Mani, and Manga) are studied under controlled conditions (32 °C ± 0.1, 43% ± 1 r.h., L: D 12:12). The results showed that males from Niamey and Parakou lived longer, while females from Niamey and Diébougou had a statistically high longevity. The larval survival rate of the Niamey strain was significantly lower than Manga, Parakou, and Navrongo. The Niamey strain recorded adults compared to the other strains. In terms of weight, the females and males from Banfora and Niamey were statistically heavier than other strains. At the end of the study, S. niger' strains showed different morphologies in terms of weight. Furthermore, adult longevity, larval survival rate, and emergence rate were strain dependent.

The Growth and Survival of the European Lobster (Homarus gammarus Linnaeus, 1758) Larvae and Juveniles in a Recirculating System

In this study, the growth and survival of H. gammarus larvae and juveniles were investigated in two different consecutive trials. In the first trial, newly hatched lobster larvae were raised in 100 liter cylindro-conical tanks in triplicate. Each tank was stocked with 150 lobster larvae (a total of 450 larvae) and the growth and survival of larvae at the end of stage IV were determined. In the second trial, the growth and survival of juvenile lobsters fed on three different diets were determined for a period of 102 days using an integrated recirculating system with 10% daily water renewal. For this purpose, a total of 3 different diets including a mollusk based (M), a crustacean based (C) and a commercial seabass diet (L) were prepared. A total of 135 juvenile lobsters, 45 for each treatment were used for the juvenile growth trial. At the end of the larval growth experiment, the mean carapace and total length of Stage IV larvae were 5.255±0.052 mm and 13.027±0.486 mm, respectively, with no significant differences within tanks (p&gt;0.05) and the mean survival rate of lobsters was 13.11%. In the juvenile growth trial, the highest carapace length was 1.371±0.023 cm in treatment C, followed by 1.251±0.039 cm and 1.187±0.095 cm in treatment M and L, respectively. At the end of 102 days, the mean survival rates of juvenile lobsters were %98.7, %80 and %53.3 in treatments C, M and L, respectively. The most successful diet for juvenile lobsters, with respect to growth and survival, was the crustacean based diet. The findings of this study provide information to help improve the growth and survival rates of larval and juvenile H. gammarus in captivity.

A method for in-situ assessment of soybean suitability to Clanis bilineata tsingtauica Mell and selecting for rearing specialized varieties

Abstract Clanis bilineata tsingtauica Mell (CBT) is a traditional edible insect. This study aimed to (1) establish an in-situ procedure for determining the suitability of soybean varieties for CBT rearing and (2) identify soybean varieties that are most conducive to CBT rearing. We developed two isolation rearing methods: the first employs mesh bags as isolation rearing tools in net houses (BIRN) and fields (BIRF), and the second uses net houses directly as isolation rearing tools (IRN). The suitability of fourteen soybean varieties with different maturity groups to CBT was assessed. Based on F values and genetic variation coefficients from single-factor and combined variance analyses across various environments, the weight of 15-day-old larvae was identified as the primary suitability indicator for BIRN and BIRF, and the 25-day-old larvae weight per plot was selected as the key indicator for IRN. BIRN and BIRF methods offer advantages such as moderate cost and high throughput, completing evaluations in just one-sixths of the consumable expenses required by IFN. IRN method more accurately reflects actual production condition, with larvae reared on mid-late maturing, lodging-resistant soybean varieties achieving significantly higher larval weights than those reared on other types of soybean varieties. BIRN and BIRF methods evaluate soybean varieties suitability for CBT primarily based on larval weight, whereas IRN considers both larval weight and larval survival rate. Thus, IRN provides a comprehensive assessment of soybean varieties suitability for CBT. BIRN and BIRF allow for multiple evaluations annually with low consumable expenses, while IRN can be employed to select varieties based on initial screening results from BIRN and BIRF. The combination of mesh bag and net house isolation rearing methods facilitates the identification of specialized soybean varieties for CBT rearing. By integrating both methods, two soybean varieties, NN18-25 and NN1138-2, were specifically identified optimal for CBT larval rearing.

Genetic Transformation of Torenia fournieri L. with the Bacillus thuringiensis Cry1Ab Gene Confers Resistance to Mythimna separata (Walker).

Torenia fournieri L. is a popular ornamental plant in the genus Torenia, widely used in commercial landscaping, especially during the summer. Additionally, Torenia has served as a model ornamental plant in many studies exploring ornamental characteristics and pest control through genetic engineering. To date, no research has been reported on developing insect-resistant Torenia expressing genes from Bacillus thuringiensis (Bt). In this study, a recombinant vector carrying the Cry1Ab gene from Bt, pBI121-Cry1Ab, was constructed and transferred into T. fournieri via Agrobacterium tumefaciens-mediated transformation. A total of 13 shoots survived on the kanamycin selection medium, among which four putative transgenic lines, designated L1, L2, L7, and L11, were molecularly confirmed by PCR and Southern blot analysis, indicating successful integration of the Cry1Ab gene into the genomes of these lines. Quantitative real-time PCR and ELISA results further verified the successful expression of the Cry1Ab gene in the leaves of all four transgenic lines. Insect bioassay results demonstrated that all four transgenic lines showed strong resistance to the insect pest, Mythimna separata, with mortality rates ranging from 59.9% to 100.0%, in contrast to a larval mortality rate of 16.2% in the wild-type Torenia. Additionally, these transgenic lines significantly decreased in larval survival rates compared to those fed on wild-type plants. Furthermore, these transgenic lines activated superoxide dismutase (SOD) activity at 12 and 24 h, and catalase (CAT) activity at 72 h, while suppressing SOD activity at 72 h, and peroxidase (POD) activity over time. Our findings indicate that these transgenic lines exhibit high resistance to the insect pest and provide new insights into controlling insect pests in ornamental plants through genetic approaches.

Bioconversion of aflatoxin-contaminated groundnut press cake by larvae of black soldier fly Hermetia illucens results in a complete mass balance for aflatoxin B1

Groundnuts are considered as one of the most important cultivated food crops globally. Groundnuts are used for vegetable oil production, which generate a variety of by-products, such as peanut press cake (PPC). Groundnuts are sensitive to infection by aflatoxigenic fungi. Aflatoxins are highly toxic to both humans and livestock, and contaminated crops containing high aflatoxin concentrations are deemed unsafe for consumption and trade. Innovative aflatoxin management strategies are needed and the insect production sector could be such a solution. Larvae of the black soldier fly (BSFL) were exposed to a PPC diet naturally contaminated with aflatoxins. After an exposure lasting eleven days, data on larval survival and biomass were collected. The PPC, BSFL and the residual material were analysed by LC-MS/MS to determine the concentration of eight different aflatoxins. A bio-accumulation factor and a molar mass balance were calculated. BSFL survival and biomass were not affected by exposure to the aflatoxin-contaminated PPC diet. The aflatoxins did not accumulate in the insect body, providing a promising outlook for the safety of rearing insects on aflatoxin contaminated PPC with the purpose of using them as food- and/or feed. Aflatoxin B1 (AFB1) was the dominant compound found in PPC. Formation of aflatoxicol, aflatoxin P1, and aflatoxin M1 occurred and taking these metabolites into account, a complete molar mass balance, thus full recovery, for AFB1 was obtained. This differs from previous studies using artificially spiked substrates in which 17–38% was recovered. This calls for additional studies comparing naturally contaminated with artificially spiked feedstuff.

Antimicrobial activity of iron-depriving pyoverdines against human opportunistic pathogens

The global rise of antibiotic resistance calls for new drugs against bacterial pathogens. A common approach is to search for natural compounds deployed by microbes to inhibit competitors. Here, we show that the iron-chelating pyoverdines, siderophores produced by environmental Pseudomonas spp., have strong antibacterial properties by inducing iron starvation and growth arrest in pathogens. A screen of 320 natural Pseudomonas isolates used against 12 human pathogens uncovered several pyoverdines with particularly high antibacterial properties and distinct chemical characteristics. The most potent pyoverdine effectively reduced growth of the pathogens Acinetobacter baumannii, Klebsiella pneumoniae, and Staphylococcus aureus in a concentration- and iron-dependent manner. Pyoverdine increased survival of infected Galleria mellonella host larvae and showed low toxicity for the host, mammalian cell lines, and erythrocytes. Furthermore, experimental evolution of pathogens combined with whole-genome sequencing revealed limited resistance evolution compared to an antibiotic. Thus, pyoverdines from environmental strains have the potential to become a new class of sustainable antibacterials against specific human pathogens.

Silencing ACE1 Gene with dsRNA of Different Lengths Impairs Larval Development in Leptinotarsa decemlineata.

In the search for effective strategies to control the Colorado Potato Beetle, RNA interference technology has emerged as a promising method due to its capacity to suppress genes selectively. Factors such as the target gene and double-stranded RNA (dsRNA) length are critical for optimizing gene silencing efficiency. In this study, we designed and synthesized in vitro dsRNAs of varying lengths targeting the ACE1 gene, which encodes the AChE1 isoform of acetylcholinesterase in the beetle. All tested dsRNA lengths (222 bp, 543 bp, 670 bp, and 870 bp) promoted transcript reduction. The 670 bp dsRNA was the most effective, reducing transcript levels by approximately 40% by day seven, followed by the 543 bp dsRNA. No significant differences were observed between the 222 bp and 870 bp dsRNAs. Furthermore, all of the dsRNA lengths resulted in reduced weight gain and increased mortality in larvae, with the 670 bp dsRNA showing the highest mortality rate, leaving only 63% larval survival, a trend that persisted through day nine. These findings emphasize that dsRNA length is a key factor in the silencing response, underscoring the importance of selecting the optimal length while considering the gene's target, stability, and delivery methods. This study contributes to establishing design criteria for dsRNA, aiding in the development of more effective and sustainable pest management strategies.